The various embodiments described herein relate to an improved optical touch panel and more particularly to an infrared (IR) touch panel having surface mount technology (SMT) components such as thin film resistors or the like.
A variety of touch panel technologies are presently in existence, including resistive technology, capacitive technology, surface acoustical wave (SAW) technology, infrared (IR) technology, etc.
In the case of IR touch panel technology, infrared emitter/collector pairs are used to project an invisible grid of light a small distance over the surface of the panel. When a beam is interrupted, the absence of the signal at the collector is detected and converted to touch coordinates (e.g., X/Y rectangular coordinates). Since the method of determining the presence of an object is optical instead of electrical or mechanical, IR touch panels are not as sensitive to damage as some technologies, such as resistive and capacitive technologies.
The structure of a conventional optical touch panel is disclosed in U.S. Pat. No. 6,597,508, which is incorporated herein by reference. FIG. 1 depicts a conventional optical touch panel 101 as shown in the patent. The optical touch panel 101 comprises a plurality of light-emitting elements (e.g., LEDs) 110 arranged along two adjacent sides of a rectangular position-detecting surface 150 and a plurality of light-receiving elements (e.g., photo transistors) 130 arranged along the other two sides of the rectangular position-detecting surface 150 such that the light-emitting elements 110 are positioned opposite to the respective light-receiving elements 130 and the position-detecting surface 150 is positioned between the light-emitting elements 110 and the light-receiving elements 130.
A control block 140 causes the light-emitting elements 110 to emit light beams sequentially from left to right and from top to bottom. Moreover, the control block 140 causes the light-receiving elements 130 to receive light beams from the respective light-emitting elements 110 positioned opposite thereto. The light beams of the light-emitting elements 110 are sequentially scanned across the position-detecting surface 150 such that optical paths are formed on the position-detecting surface 150 in a grid pattern.
The touch coordinates can be determined according to which light-emitting elements 110 emit light beams and which light-receiving elements 130 sense such light beams during a scan cycle. When an object (e.g., a pointing device such as a touch pen or a finger) 170 is positioned on the position-detecting surface 150 as shown in FIG. 1, the object 170 blocks optical paths, thereby hindering light beams from the corresponding light-emitting elements 110 from reaching the corresponding light-receiving elements 130 positioned opposite to the light-emitting elements 110. As a result, the control block 140 determines the position of the object 170 in terms of two-dimensional coordinates (e.g., X/Y rectangular coordinates) based on information from the light-receiving elements 130 with respect to received light beams. If the object 170 also blocks the infrared light of adjacent rows and columns of the grid pattern, the intended center position can be obtained by averaging the coordinate information received by the relevant computing device.
The optical touch panel 101 requires an optical gate (i.e., light gate) for each light-receiving element 130 for the purpose of isolating ambient light (e.g., sunlight). Such optical gate is necessary to prevent erroneous light detection from being caused by ambient light, which potentially can hinder proper light detection from the corresponding light-emitting element 110. However, the conventional assembly process for an optical gate requires error-prone human assembly. Moreover, a conventional optical gate design can be expensive. Accordingly, it would be advantageous to provide a novel and less expensive solution for forming an optical gate for each light-receiving element without human assembly for the optical gate.